Clovis' rucaparib made a strong claim Saturday to unseat AstraZeneca's Lynparza as the most effective PARP inhibitor treatment for a genetically defined segment of previously-treated ovarian cancer patients.

Clovis shares closed Friday at $92.44, but the stock could fall Monday given lung cancer data at ASCO acknowledged as "disappointing" by one one sell-side analyst with a history of being very bullish about the company.

In a mid-stage study of patients with advanced ovarian cancer carrying the mutated BRCA gene, treatment with Clovis' rucaparib yielded a response rate of 82%. Ten percent of patients had complete resolution of their tumors. Median progression-free survival was 9.4 months.

Another 45% of ovarian cancer patients with "BRCA-like" mutations responded to rucaparib. Median progression-free survival in these patients was 7.1 months.

Mid-stage studies of rucaparib are still ongoing, but Clovis set plans to seek regulatory approval for rucaparib next year. The company estimates 25% of ovarian cancer patients carry the BRCA mutation, with another 35% of patients carrying "BRCA like" mutations also amenable to treatment with rucaparib.